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POJava: Pass by reference / ListIterator.add()
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copied!<p>Java doesn't pass variables by reference. In that case, how do data structures like <code>ListIterator</code> make changes to their corresponding list?</p> <p>Here is an example iterator I am writing:</p> <pre><code>public class OdpIterator<E> implements ListIterator<E> { private OdpList<E> list; private int cursor; public OdpIterator(OdpList<E> list) { this.list = list; } @Override public void add(E arg0) { list.add(arg0); } </code></pre> <p>But then when I try to change <code>list</code> through <code>add()</code>, it doesn't change the underlying list, so the following test fails:</p> <pre><code>OdpList<Integer> list = new OdpList<Integer>(); ListIterator<Integer> iter = list.listIterator(); iter.add(42); assertTrue(list.contains(42)); </code></pre> <p>OdpList add: I believe that it is correct, as it passes its unit tests.</p> <pre><code>@Override public boolean add(E arg0) { ListCell<E> cell = new ListCell<E>(arg0); if (size() > 0) { //if something is already in the list tail.setNext(cell); tail = cell; } else { head = cell; tail = cell; } return true; } </code></pre> <p>ListCell constructor:</p> <pre><code>public class ListCell<T> { public ListCell(T arg0) { this.datum = arg0; next = null; } } </code></pre> <p>OdpList listIterator:</p> <pre><code>@Override public ListIterator<E> listIterator() { return new OdpIterator<E>(this); } </code></pre> <p>OdpList contains:</p> <pre><code>@Override public boolean contains(Object arg0) { return indexOf(arg0) == -1; } @Override public int indexOf(Object arg0) { return findAfter(head, arg0, 0); } private int findAfter(ListCell<E> o, Object search, int soFar) { if (o == null) { return -1; } if (o.getDatum() == null && search != null) { return findAfter(o.getNext(), search, soFar + 1); } if ((o.getDatum() == null && search == null) || o.getDatum().equals(search)) { return soFar; } return findAfter(o.getNext(), search, soFar + 1); } </code></pre> <p>How do I do this? Or am I misunderstanding how iterators work?</p>

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